A C-plane GaN substrate only mildly restricts the shape and dimension of a nitride semiconductor device formed on the substrate. The variation of an off-angle on the main surface of the substrate is suppressed. In the C-plane GaN substrate: the substrate comprises a plurality of facet growth areas each having a closed ring outline-shape on the main surface; the number density of the facet growth area accompanied by a core among the plurality of facet growth areas is less than 5 cm−2 on the main surface; and, when any circular area of 4 cm diameter is selected from an area which is on the main surface and is distant by 5 mm or more from the outer peripheral edge of the substrate, the variation widths of an a-axis direction component and an m-axis direction component of an off-angle within the circular area is each 0.25 degrees or less.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A C-plane GaN substrate comprising: a main surface; and a plurality of facet growth areas each having a closed ring outline-shape on the main surface, wherein a number density of the facet growth area accompanied by a core among the plurality of facet growth areas is less than 5 cm −2 on the main surface, the number density is the number of the facet growth areas accompanied by cores that are observed on the main surface in a unit area, in any circular area of 4 cm diameter formed on the main surface inside a circle disposed at 5 mm from the outer peripheral edge of the substrate, a variation range of an off-angle with respect to an a-axis direction component and with respect to an m-axis direction component within the circular area is 0.25 degrees or less for each component, said off-angle being a tilt angle of a normal vector to the main surface with respect to a c-axis as a reference, and the substrate includes either or both of silicon and germanium.
2. The C-plane GaN substrate according to claim 1 , wherein the substrate has a C-plane growth area lying outside the plurality of facet growth areas on the main surface.
3. The C-plane GaN substrate according to claim 1 , wherein the number density of the facet growth area accompanied by an inversion domain among the plurality of facet growth areas is 0 cm −2 on the main surface.
4. The C-plane GaN substrate according to claim 1 , wherein the sum of the areas of all the facet growth areas present on the main surface is 70% or more of the area of the main surface.
5. The C-plane GaN substrate according to claim 1 , wherein the plurality of facet growth areas are at least partially regularly arranged.
6. The C-plane GaN substrate according to claim 5 , wherein the arrangement of the facet growth areas regularly arranged among the plurality of facet growth areas is a square lattice arrangement or a triangle lattice arrangement.
7. The C-plane GaN substrate according to claim 1 , wherein the substrate has an electrical resistivity of 0.1 Ω·cm or less.
8. A method for producing a nitride semiconductor device, comprising a step of preparing the C-plane GaN substrate according to claim 1 , and a step of epitaxially growing at least one nitride semiconductor layer on the prepared C-plane GaN substrate.
9. A method for producing an epitaxial wafer, comprising a step of preparing the C-plane GaN substrate according to claim 1 , and a step of epitaxially growing at least one nitride semiconductor layer on the prepared C-plane GaN substrate.
10. The C-plane GaN substrate according to claim 1 , wherein the number density of the facet growth area corresponds to the number of dot-shaped depressions observed on the main surface in the unit area.
11. A C-plane GaN substrate having a diameter of 95 to 105 mm comprising: a main surface; and a plurality of facet growth areas each having a closed ring outline-shape on the main surface, wherein a number density of the facet growth area accompanied by a core among the plurality of facet growth areas is less than 5 cm −2 on the main surface, the number density is the number of the facet growth areas accompanied by cores that are observed on the main surface in a unit area, and in an area on the main surface inside a circle disposed at 5 mm from the outer peripheral edge of the substrate, a variation range of an off-angle with respect to an a-axis direction component and with respect to an m-axis direction component is 0.5 degrees or less for each component, said off-angle being a tilt angle of a normal vector to the main surface with respect to a c-axis as a reference.
12. The C-plane GaN substrate according to claim 11 , wherein the substrate has a C-plane growth area lying outside the plurality of facet growth areas on the main surface.
13. The C-plane GaN substrate according to claim 11 , wherein the number density of the facet growth area accompanied by an inversion domain among the plurality of facet growth areas is 0 cm −2 on the main surface.
14. The C-plane GaN substrate according to claim 11 , wherein the sum of the areas of all the facet growth areas present on the main surface is 70% or more of the area of the main surface.
15. The C-plane GaN substrate according to claim 11 , wherein the plurality of facet growth areas are at least partially regularly arranged.
16. The C-plane GaN substrate according to claim 15 , wherein the arrangement of the facet growth areas regularly arranged among the plurality of facet growth areas is a square lattice arrangement or a triangle lattice arrangement.
17. The C-plane GaN substrate according to claim 11 , wherein the substrate is added with either or both of silicon and germanium.
18. The C-plane GaN substrate according to claim 11 , wherein the substrate has an electrical resistivity of 0.1 Ω·cm or less.
19. A method for producing a nitride semiconductor device, comprising a step of preparing the C-plane GaN substrate according to claim 11 , and a step of epitaxially growing at least one nitride semiconductor layer on the prepared C-plane GaN substrate.
20. A method for producing an epitaxial wafer, comprising a step of preparing the C-plane GaN substrate according to claim 11 , and a step of epitaxially growing at least one nitride semiconductor layer on the prepared C-plane GaN substrate.
21. A C-plane GaN substrate comprising: a main surface; and a plurality of facet growth areas each having a closed ring outline-shape on the main surface, wherein a number density of the facet growth area accompanied by a core among the plurality of facet growth areas is less than 5 cm −2 on the main surface, the number density is the number of the facet growth areas accompanied by cores that are observed on the main surface in a unit area, in any circular area of 4 cm diameter formed on the main surface inside a circle disposed at 5 mm from the outer peripheral edge of the substrate, a variation range of an off-angle with respect to an a-axis direction component and with respect to an m-axis direction component within the circular area is 0.25 degrees or less for each component, said off-angle being a tilt angle of a normal vector to the main surface with respect to a c-axis as a reference, and the number density of the facet growth area accompanied by an inversion domain among the plurality of facet growth areas is 0 cm −2 on the main surface.
22. A C-plane GaN substrate comprising: a main surface; and a plurality of facet growth areas each having a closed ring outline-shape on the main surface, wherein a number density of the facet growth area accompanied by a core among the plurality of facet growth areas is less than 5 cm −2 on the main surface, the number density is the number of the facet growth areas accompanied by cores that are observed on the main surface in a unit area, in any circular area of 4 cm diameter formed on the main surface inside a circle disposed at 5 mm from the outer peripheral edge of the substrate, a variation range of an off-angle with respect to an a-axis direction component and with respect to an m-axis direction component within the circular area is 0.25 degrees or less for each component, said off-angle being a tilt angle of a normal vector to the main surface with respect to a c-axis as a reference, and the sum of the areas of all the facet growth areas present on the main surface is 70% or more of the area of the main surface.
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August 21, 2017
January 8, 2019
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